Igniters for mines



NOV. 29, 1966 P, MADLENER ET AL 3,288,067

IGNITERS FOR MINES Filed Jan. 27, 1965 United States Patent 3,288,067 IGNITERS FOR MINES Paul Madlener, Karlsruhe-Durlach, and Otto` Pecksen,

Berghausen, Baden, Germany, assgnors to Industrie- Werke Karlsruhe Aktiengesellschaft, Karlsruhe, Germany Filed Jan. 27, 1965, Ser. No. 428,401 Claims priority, application Germany, May 26, 1962,

21,836; Jan. 31, 1964, .l 25,206

Claims. (Cl. 102-70) The present application is a continuation-in-part appli cation of the copending application Serial No. 281,384 filed May 15, 1963, now Patent No. 3,221,657.

'Ihe present invention relates to igniters for mines, and more particularly to an igniter for land mines which constitutes an improvement over and a further development of the igniter disclosed in said copending application. Still more particularly, the invention relates to a metal-free igniter for land mines.

The aforementioned application Serial No. 281,384 discloses an igniter which comprises a pressure-responsive llame generating device arranged to respond to a pressure differential for setting the igniter in operation. Such pressure differential is produced by an evacuated airtight container whose interior is maintained at a pressure well below atmospheric pressure and which is mounted in a position where its interior will communicate with and will actuate the flame generating device in response to rupture of its wall.

It is an important object of our invention to provide an igniter for land mines and the like which is constructed and assembled in such a way that its pressure responsive ame generating device invariably detonates the mine in response to rupture` lor breakage of the evacuated container and wherein such rupture can be caused in response to a minimal stress upon the container.

Another object of the invention is to provide a novel evacuated container for use in an igniter of the just outlined characteristics.

A further object of the invention is to provide an igniter which is free of metallic parts when it is ready to cause explosion of a mine and which can be prevented from causing accidental explosion in a very simple way.

An additional object of the invention is to provide a novel mounting for the evacuated container and to provide a novel pressure responsive flame generating device which will cause ignition of the primer charge in response to rupture of the container.

A concomitant object of the invention is to provide a novel safety device for use in an igniter of the above outlined characteristics.

Still another object of the invention is to provide a novel guide for the flame generating device and to provide a novel housing which accommodates the llame generating device and its guide.

Briey stated, one feature of our invention resides in the provision of an igniter for land mines and the like. The igniter comprises a hollow multi-section housing, a substantially circular exible diaphragm having a marginal portion sealingly secured to the housing so as to subdivide the interior of this housing into a pair of separate chambers at least one of which is sealed from the atmosphere, an evacuated container consisting of readily breakable material and mounted in the one chamber so that, in responseto rupture of the container, the diaphragm is suddenly flexed in a sense to reduce the volume of the one chamber, ame generating means comprising a primer secured to and movable with the central portion of the diaphragm and a firing pin mounted in the one chamber of the housing so as to be located in the path of the primer, and guide means for guiding the primer during movement with the diaphragm.

3,288,067 Patented Nov. 29, 1966 In accordance with a preferred embodiment of our invention, the evacuated container comprises a spherical main portion which rests on an apertured partition provided in the one chamber -of the housing and an elongated neck portion which is received in a readily deformable tubular extension of the housing. The periphery of the container defines with the internal surface of the housing at least one passage or gap through which air penetrates into the spherical portion when the neck portion of the container -breaks in response to deformation of the tubular extension, The drop in pressure is communicated through the apertured partition and to one side of the diaphragm which is then flexed and causes the primer to strike against the tiring pin with a force suicient to cause ignition of the primer charge. The resulting llame is used to set olf a detonator which ignites the main explosive charge of the mine.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved igniter itself, however, both -as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of a specific embodiment with reference to the accompanying drawings, in which:

FIG. 1 is a side elevational view of a fully assembled igniter which is constructed and assembled in accordance with our invention;

FIG. 2 is an enlarged axial section through the lower part of theigniter; and

FIG. 3 is a transverse section as seen in the directio of arrows from the line III-III of FIG. 2.

Referring to FIGS. 1 and 2, the igniter of our invention comprises a housing including three sections consisting of synthetic plastic material and bonded, screwed or otherwise securely iixed to each other. The three sections include a bottom wall 1, an intermediate wall or cylinder 2, and a top wall or cover 3. The marginal portion of a substantially circular deformable plastic diaphragm 4 is sealingly clamped between the cylinder 2 and cover 3. Actually, the marginal portion of the diaphragm 4 is sealingly received between a shouler 2a of the cylinder 2 and the axially extending annular ange 5b of a transversely extending partition 5, the latter being telescoped into the cylinder 2 and being pressed against the diaphragm 4 by the open end of the cover 3 which is provided with external threads to mate with internal threads at the upper end of the cylinder, as the parts appear in FIG. 1. The sealing action upon the marginal portion of the diaphragm 4 depends on the force with which the cover 3 is screwed into the cylinder 2.

The central portion of the diaphragm 4 is clamped between a disk y6 and a hollow sleeve-like guide element 7. The disk 6 is provided with a centrally located tapped -bore to receive a hollow externally threaded extension 7b of the guide element 7. The lower portion of the guide element 7 is readily slidably telescoped onto a hollow cylindrical element or stud 8 which is rigidly secured to or integral with the bottom wall 1. The extension 7b accommodates a small ignition cap or primer 9 and the flame which is generated on ignition of the charge in the primer 9 penetrates through the central passages of the guide element 7 `and stud 8, and is utilized to set oft' a suitable detonator for the mine, not shown.

The bott-om wall 1 and the cylinder 2 define between themselves an annular chamber 1a which communicates with radially extending p-orts 7a provided in the guide element 7 and with radially extending ports 8a provided in the stud 8. The upper end of the chamber 1a is sealed by the shoulder 2a and diaphragm 4.

The cylinder 2 is formed with a radially extending tapped bore which receives a short externally threaded plastic sleeve 10. The axis of the sleeve is normal to the axis of the cylinde-r 2, and this sleeve is sealingly secured to the cylinder by a suitable adhesive or in another way. A non-removable plunger 11 is reciprocable in the sleeve 1t) and its inner end portion carries two axially `space-d collars 12, 13 of rectangular cross section. The outer collar 12 constitutes a stop for the plunger 11 when the igniter is ready for use, and the inner collar 13 serves as a stop to prevent accidential ignition of the charge in the primer 9. The guide element 7 is provided with an out- -wardly extending annular flange or detent 14 a portion of which receives the stop 13 when the plunger 11 is held in the axial position shown in FIG. 1. This plunger is surrounded by two elastic annular sealing rings 15 (called O- rings) which may consist of silicone rubber or the like. These rings are seated `with some axial play in circumferential grooves of the plunger 11 and seal the chamber 1a from the atmosphere. The outer end of the plunger 11 is connected with an actuat-ing member here shown as a springy pull ring or eye 16 which abuts against the outer end of the sleeve 10 when the stop 13 extends into the path of the detent 14. The parts 10-14 together consittute a safety device which normally prevents such flexing of the diaphragm 4 as is necessary to bring about ignition of the prime-r charge.

The central portion of the partition 5 carries a pointed ring pin 17 whose tip faces the primer 9 and is normally spaced therefrom. The compartment 1b between the diaphragm 4 and partition S forms part of a second chamber 1c provided in the interior of the cover 3, and the partition S is provided with apertures 5a which allow air to flow from the compartment 1b -into the remainder of the chamber 1c. This chamber 1c is sealed from the atmosphere and accommodates an evacuated container or ampoule 18 which consists of unstressed vitreous or other frangible material. The -main portion of the ampoule 18 is of spherical shape and comprises a cylindrical neck portion 18a which extends with clearance into a readily flexible tubular extension 21 of the cover 3. The outer side of the neck portion 18a carries three small equidistant strips or pads 19 of synthetic plastic material, e.g., polyvinyl chloride. The strips 19 serve to properly locate the neck portion 18a and to provide gaps or passages of predetermined width and cross-sectional area (see FIG. 3), such gaps extending between the periphery of the neck portion 18a and the internal surface of the extension 21. The main (spherical) portion of the ampoule 18 is received between four cushions 20 of elastically deformable foamed plastic material. -Such cushions serve to locate and to prevent accidental 4breakage of the ampoule as well as to allow ow of air from the compartment 1b into the ampoule when the neck portion 18a breaks. For example, the maximum length of the ampoule 18 may be about 180 mm. and its interior is evacuated so that the pressure prevailing therein approximates 0.01 atmosphere absolute pressure. The upper end of the neck portion 18a (through which the air was evacuated from the ampoule 18) is sealed by melting down and by subsequent hardening.

That portion of the flexible extension 21 which projects beyond the tip of the neck portion 18a may be about 55 mm. long, and the tip of the neck portion 18a is surrounded by a sealing cap 22 which is bonded to the internal surface of the extension 21 to seal the chamber 1c from the atmosphere. The outer end face of the cap 22 is bonded to a sealing disk 23 of polyvinyl chloride or another synthetic plastic material.

If necessary, the outer end portion of the extension 21 may receive a rigid rod or antenna 24 consisting of polyethylene reinforced with glass fibers.

The bottom wall 1 comprises an outwardly extending centrally located threaded nipple 8b which is surrounded by a cupped protecting cap 25. A sealing ring 26 of `soft silicone rubber or the like is inserted between the llange of the cap and the outer side of the bottom wall 1 to provide a iluidtight sealing action in response to cornparatively small compressive stresses transmitted by the cap 25.

If the extension 21 is flexed and/ or if the antenna 24 is tilted sideways, the neck portion 18a of the ampoule 18 breaks so that the pressure in the chamber 1c decreases instantaneously. Such drop in pressure is propagated through the gaps between the strips 19, around the spherical portion of the ampoule 18 and through the apertures 5a on to the compartment 1b. As a result of such -drop in pressure at the upper side of the diaphragm 4, the latter is rapidly flexed upwardly as the parts appear in FIG. l, and the primer 9 is propelled against the tip of the tiring pin 17. The charge in the primer 9 is ignited and the tlame is propagated through the stud 8 and the nipple 8b. When the igniter is to be used in a mine, the cap 25 is removed and the nipple Sb is connected to or receives a dctonator `which then ignites the main explosive charge of the mine. The parts 9, 17 together constitute a llame generating device which will produce a flame in response to sudden flexing of the diaphragm 4 provided that the stop 13 is withdrawn from the path of the detent 14.

When the neck portion 18a breaks while the safety device including the plunger 11 is in the operative position of FIG. 1, the pressure differential at the opposite sides of the diaphragm 4 propels the primer 9 toward but short of the firing pin 17. It will be noted that the detent 14 is provided with an annular groove or recess 14a which receives a portion of the stop 13 so that the plunger 11 cannot be Withdrawn following accidental destruction of the nec-k portion 18a. In other words, and assuming `that the neck portion 18a breaks accidentally and that the plunger 11 is in the operative position of FIG, 1 in which the primer 9 is prevented from reaching the firing pin 17, there is no 'way of igniting the primer charge excepting upon forcible extraction of the stop 13 from the recess 14a of the detent`14.

It is often desirable to mount the diaphragm 4 in such a way that it allows for gradual equalization of pressures in t-he chambers 1a and 1c. Thus, and assuming that the charge in the primer 9 failed to produce a llame when the primer was propelled against the firing pin 17, such gradual equalization of pressures will allow for Safe dismantling of the igniter because the diaphragm 4 will re= turn to the position of FIG. 1 as soon as the pressure pre= vailing in the chamber 1c equals or approximates the pressure in the chamber 1a.

The weight of the diaphragm 4 and of the parts 6, 7 which are connected thereto is preferably negligible so that the primer 9 is not likely to strike against the tiring pin 17 in response to accidental shaking or jarring of the igniter. Such accidental ignition is even less likely because the guide element 7 is slidably telescoped on the stud 8.

In order to attach the igniter to the mine, the operator removes the cap 25 and inserts a dctonator in the nipple 8b. This nipple is then screwed into the mine so that the dctonator will cause an explosion of the main charge as soon as the device 9, 17 produces a flame which is propagated through the stud 8. When the mine is properly camouaged or concealed, the person in charge exerts a pull on the eye 16 so that the stop 13 is withdrawn from the path of the detent 14. At the same time, the operator detaches the eye 16 from the plunger 11 so that the eye serves as a proof that the mine is ready to explode in response to breakage of the ampoule 18. The manner in which the eye 16 can be detached from the plunger 11 is clearly shown in FIG. 2. The eye 16 preferably consists of steel but the remaining parts of the igniter do not contain any metallic material to avoid detection of a mine which is equipped with our igniter.

The ratio between the volume of the chamber 1c and the Volume of the ampoule 18 is selected in such a way that the drop in pressure on breakage of the neck portion 18a invariably results in sudden flexing of the diaphragm 4 such .as will suice to propel the primer 9 against the pin 17.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applicationsv without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An igniter for mines, comprising -a hollow housing; a flexible diaphragm mounted in and subdividing the interior of said housing into a pair of separate chambers at least one of which is sealed from the atmosphere; an evacuated container of breakable material mounted in said one chamber so that, in response to rupture of said container, the diaphragm is suddenly flexed by suction action in a sense to reduce the volume of said one chamber; and flame generating means including -a tiring member and a primer member, one of said members being mounted on and being movable by said diaphragm and the other member being mounted in said housing in the path of said one member.

2. An igniter for land mines and the like, comprising a hollow multi-section housing; a substantially circular exible diaphragm having a marginal portion sealingly secured in said housing so as to subdivide the interior of the housing into a pair of separate chambers at least one of which is sealed from the atmosphere;` an evacuated container consisting of readily breakable material and mounted in said one chamber so that, in response to rupture of said container, the diaphragm is suddenly flexed in a sense to reduce the volume of said one chamber; ame generating means comprising a firing member and a primer member, one of said members being fixed to the central portion of said diaphragm and the other member being tixedly mounted in said one chamber of the housing so as to be located in the path of said one member; and guide means for guiding said one member `during movement with said diaphragm.

3. A metal-free igniter for mines, comprising a hollow multi-section housing; an apertured partition in said housing; a substantially circular flexible diaphragm having a marginal portion sealingly secured to said housing so as to divide the interior of the housing into a rst chamber containing said partition and a second chamber, said housing having a deformable tubular extension communicating with said rst chamber and at least said first chamber being sealed from the atmosphere; an evacuated container comprising a spherical portion received with clearance in said rst chamber between said partition and said extension, and a neck portion extending with clearance into said extension, said container consisting of readily breakable material so that, in response to deformation of said extension, said neck portion breaks and the pressure in Vsaid first chamber decreases whereby the diaphragm is suddenly flexed in a sense to reduce the volume of said first chamber; ame generating means comprising a tiring member and'a primer member, one of said members being secured to the central portion of and being movable with said diaphragm and the other member being secured to said partition in the path of said one member so that the charge of said primer member is ignited when said tiring member is brought in contact with said primer member in response to breakage of said container; and guide means for said one member of said ame generating means, said guide means including a first hollow cylindrical element fixed to the central portion of said diaphragm and a second hollow cylindrical element secured to said housing and located in said second charnber, one of said elements being slidably telescoped into the other thereof so that said iirst element is guided in a straight path when said diaphragm is flexed in response to breakage of said container.

4. An igniter as set forth in claim 3, further comprising a safety device for normally preventing engagement of said tiring member with said primer member, said safety device comprising detent means xed to and movable with said rst hollow cylindrical element of said guide means, said detent means being located in said second chamber, and stop means reciprocably received in said second chamber and normally located in the path of -said detent means so as to limit the extent of movement of said one member of said ame generating means in response to exing of said diaphragm.

5. An igniter as set forth in claim 4, wherein said safety device further comprises a non-withdrawable plunger connected with said stop means and extending from said housing, and actuating means detachably secured to said plunger externally of said housing.

6. An igniter as set forth in claim 5, wherein said actuating means comprises a metallic eye and wherein said detent means is provided with a groove to receive a portion of said stop means when the container breaks while said stop means extends into the path of said detent means.

7. A non-metallic igniter for land mines and the like, comprising a hollow multi-section housing; a substantially circular ilexible diaphragm having a marginal portion sealingly secured in said housing so as to subdivide the interior of the housing into a pair of separate charnbers at least one of which is sealed from the atmosphere; an evacuated container consisting of readily breakable vitreous material and mounted in -said one chamber so that, in response to rupture of'said container, the diaphragm is suddenly tiexed in a sense to reduce the volume of said one chamber; flame generating means comprising a firing member and a primer member, one of said members -being tixed to the central portion of said diaphragm and the other member being fxedly mounted in said one chamber of the housing so as to be located in the path of said one member; and guide means for guiding said one member during movement with said diaphragm, said primer member comprising a charge which is ignited on impact against said ring member and said guide means dening a passage through which the flame resulting from ignition of said charge is propagated to operate the detonator of a mine.

8. An igniter as set forth in claim 7, further comprising detachable cap means for normally sealing said passage from the atmosphere and a safety device including a plunger movable substantially radially of said diaphragm and extending into the other of said chambers, said safety device further comprising detent means tixed to said diaphragm in said other chamber and a stop secured to said plunger and normally extending into the path of said detent means to prevent ignition of said charge in response to accidental rupture of said container by maintaining said i'ring member out of contact with said charge.

9. An igniter for mines, comprising a hollow housing; a flexible diaphragm mounted in and subdividing the interior of said housing into a pair of separate chambers each of which is sealed from the atmosphere; an evacuated container of breakable material mounted in said one chamber so that, in response to rupture of said container, the diaphragm is suddenly exed in a sense to reduce the volume of said one chamber; and flame generating means including a tiring member and a primer member, one of said members being mounted on and being movable by said diaphragm and the other member being mounted in said housing in the path of said one member, said diaphragm being mounted in such a way that the pressure prevailing in said chambers is gradually equalized following the rupture of said container in the event that such rupture does not result in generation of a flame.

10. An igniter for land mines and the like, comprising a hollow multi-section housing; a substantially circular ilexible diaphragm having a marginal portion sealingly secured in said housing so as to subdivide the interior of the housing into a pair of separate chambers at least one of which is sealed from the atmosphere; an evacuated container consisting of readily breakable material and mounted in said one chamber so that, in response to rupture of said container, the diaphragm is suddenly flexed in a sense to reduce the volume of said one chamber; flame generating means comprising a firing member and a primer member, one of said members being fixed to the central portion of said diaphragm and the other member being Xedly mounted in said one chamber of the housing so as to be located in the path of said one member; and hollow cylindrical guide means References Cited by the Examiner UNITED STATES PATENTS 2,923,237 2/1960 Bleikamp 102-8 3,221,657 12/1965 Madlener et al 102-70 FOREIGN PATENTS 1,200,516 6/1959 France.

BENJAMIN A, BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

1. AN IGNITER FOR MINES, COMPRISING A HOLLOW HOUSING; A FLEXIBLE DIAPHRAGM MOUNTED IN SAID SUBDIVIDING THE INTERIOR OF SAID HOUSING INTO A PAIR OF SEPARABLE CHAMBERS AT LEAST ONE WHICH IS SEALED FROM THE ATMOSPHERE; AN EVACUATED CONTAINER OF BREAKABLE MATERIAL MOUNTED IN SAID ONE CHAMBER SO THAT, IN RESPONSE TO RUPTURE OF SAID CONTAINER, THE DIAPHRAGM IS SUDDENTLY FLEXED BY SUCTION 